Electrostatic alphanumerical printer with image transfer mechanism



March 6, 1962 F. A. scHWERTZ 3,023,731

ELECTROSTATIC ALPHANUMERICAL PRINTER WITH IMAGE TRANSFER MECHANISM FiledJune 6. 1957 2 Sheets-Sheet 1 I N VEN TOR. @me-,Wag A. Sci/M5972.

Sunny @oase March 6, 1962 F A. scHwl-:RTZ

ELECTROSTATIC ALPHANUMERICAL PRINTER WITH IMAGE TRANSFER MECHANISM 2Sheets-Sheet 2 Filed June 6. 1957 .Lv -F.Lll E @2 z V .M V .U LI an; mw..n 33 A mw l M m Q y QQQM. IW' 7 United States Patent() 3,023,731ELECTROSTATIC ALPHANUMERICAL PRINTER WITH IMAGE TRANSFER MECHANISMFrederick A. Schwertz, Pittsford, N.Y., assigner to The Haloid Company,Rochester, N.Y., a corporation of New York n Filed June 6, 1957,Ser.No.'664,138 17 Claims. (Cl. V11S-'625) The present invention relatesgenerally to high-speed recording of computational data'and moreparticularly to apparatus adapted jto record alphanumerical informationelectrostatically as "latent images on a continuous insulating medium,which images are thereafter developed and transferred to `an ordinaryprinting paper.

The written or pr'rnted 'values yielded by the output system of'anelectronic computer may assume any one of several forms depending on'the nature of the data and its eventual use. With vthe recentdevelopment of highspeed computer machines and other mechanical andelectronic devices which produce data at high rates of speed, there hasarisen a concomitant need for high-speed recording devices, forotherwise the printer or other recording mechanism may act to retard theoperation of'the entire machine. Where vthe production rate of outputdata exceeds the 'capacity of the output printer, the usual practice isto store the output information as rapidly as it is produced and to feedit from storage to the printer as rapidly as the printer will accept'thein'formation In the copending applications entitled ElectrostaticRecording of Information, Ser. No. 623,327, filed November 20, 1956 (nowabandoned), and High-Speed Electrostatic Alphanumerical Printer, Ser.No. 664,137, tiled June 6, 1957 (now issued as Patent No. 2,919,967),there is described a novel electrostatic image-forming technique forrecording alphanumerical information, which technique overcomes many ofthe drawbacks characteristic of known mechanical and optical printers.

The electrostatic image-forming process as disclosed in said copendingapplications makes possible the transfer of electrostatic images to arecording medium at eX- tremely high speeds, these images beingsubsequently rendered visual by methods conventional in the Xerographicart. Digital computer switching circuits co-acting with theelectrostatic image-forming apparatus permit the logical spacialordering of electrostatic images which owe their origin to informationpulses received serially in time.

In the art of Xerography in its electrophotographic aspects, anelectrostatic charge applied to the surface of a photoconductiveinsulating layer is selectively dissipated by exposure to a pattern oflight and shadow to be recorded, thereby forming on the surface of theinsulating layer an electrostatic latent image corresponding to saidpattern. An image formed in this fashion may be developed by thedeposition of finely divided material in conformity with the chargepattern and thereafter fixed by fusing the powder on the surface of aprint to which the powder pattern has been transferred. A detaileddescription of the Xerographic technique and of the apparatus involvedin developing and fixing pictures may be found in the U.S. Patent toCarlson No. 2,297,691.

In the apparatus disclosed in the copending applications asdistinguished from Xerography in its electrophotographic aspects,physical symbols or characters rather than light patterns are recordedas electrostatic images. The images are then developed by depositing afinely divided powder or an ink mist, the resulting visible images beingmade permanent by fusing or drying. The electrostatic images areproduced by character faces or symbolshaped electrode elements which arebrought in close Mice proximity to an yinsulating surface, Vsuch as aweb of dielectric material. The web is electrostically pre'charged by anintense electric field to 'a point somewhat below critical stress value.Alternatively a static bias voltage may be 'applied to bring 'theapplied feldto the point of incipient breakdown.

Transfer of the configuration of the symbol or character from theVshaped electrode to the insulating web is effected by the use of arelatively low potential triggering pulse which raises the electricfield above the critical stress value toiproduce a field discharge inthe Vspace between the insulating web and the electrode. The dischargeaction gives rise to the formation of an electrostatic pattern of thesymbol on the insulating surface. Electronic switching circuits'areassociated with the electrostatic apparatus to supply trigger pulsesthereto in accordance with information received electrically from adigital vcomputer or other signal source. This process is now known asTesiprinting (Transfer Electro Static Image).

In the copending applications, alphanumerical characters are formed withthe aid of raised character-metal elements disposed about thecircumference of a cylindrical drum, one column of characters beingprovided for each column of the printed page. The characters are causedto pass in the vicinity of a paper web by rotating the character drum ata constant angular velocity. Disposed above the paper is an array ofelectrodes, one for each column tobeprinted. When the selected characterpassesv beneath a chosen electrode, a high-voltage pulse is applied toeffect a field discharge between the selected character and the web at aposition corresponding to that of the chosen electrode. y

The field discharge causes the formations of latent electrostatic imageson the paper web passing over the character drum. When the web iswithdrawn from the electrostatic apparatus, it passes through adevelopment mechanism wherein the invisible electrostatic images arerendered visible by depositing thereon `a finely divided powder whichadheres to the charged image areas. To

romote development, the particles are preferably charged bytriboelectric or other means. Thereafter the powder images are fusedonto the paper to form a permanent print of the information recorded.

Thus in the electrostatic printing devices of the type described in theabove-identified copending applications, the paper web must possesscharacteristics rendering it suitable for supporting an electrostaticimage as well as providing a printing surface for a powder image. Thisrequires the use of a carefully dried paper or a paper specially treatedto afford a recording surface of high resistivity to sustain anelectrostatic charge. This requirement precludes the use of ordinarypaper and adds materially to the cost of the operation.

In view of the foregoing it is the principal object of the presentinvention to provide a non-optical electrostatic printer for recordingalphanumerical information wherein the information may be printed oninexpensive paper of ordinary quality. Y

More particularly, it is an object of this invention to provide ahigh-speed electrostatic printer wherein electrostatic images may beformed on a continuous flexible web of insulating material, which imagesare then transferred to ordinary paper. A significant feature of theinvention is the fact that the continuous web may be reusedindefinitely, the image thereon being erased after transfer is effected.

Also, an object of the invention is to provide a character drum for anelectrostatic printer, which drum is constituted by a bank of characterVrings insulated from each other, whereby the rings may be separatelypulsed. In accordance with an important feature of the invention,

each character ring on the drum is associated with a commutator ringcooperaitng with an electrode spaced therefrom. A field discharge isproduced between the character ring and an associated endless metal belthaving an insulating layer thereon, the lines of stress extendingthrough a gap between the electrode and the commutator ring.

Also an object of the invention is to provide an electrostatic printerwherein alphanumerical images are simulated by selective activation ofan array of electrode pins carried on stationary matrix type recordingheads.

Briefly stated, in an electrostatic apparatus for recording and printingalphanumerical information in accordance with the invention, theinformation received from a computer or other data source is recordedelectrostatically on an endless medium having an insulating surface ofhigh resistivity for sustaining electrostatic charges. This endlessmedium may be constituted by a continuous belt of insulating material ora continuous metal belt having an insulating layer thereon.Alternatively, the endless medium may take the form of a rotary metalliccylinder having an insulating layer coated thereon.

A character-forming station is supported in spaced relation to theinsulating surface of the recording medium to define an air gaptherebetween. The character station includes character-forming elementsadapted to produce latent electrostatic images on said medium whenvoltages are applied thereto effecting a field discharge in the air gap.The station may be constituted by a rotary drum containing rings ofraised-character elements which may be selectively aligned with themedium. Alternatively, the character-forming elements may be constitutedby an array of pins which may be selectively actuated by pulses to buildup the character by a pattern of dots.

The medium is moved relative to the character station to producesuccessive lines of characters thereon. A charging station is disposedin advance of the character station to pre-stress the medium to auniform potential and thereby erase previously made electrostatic latentimages. The medium after recording passes through a developer section toform powder images. 'Ihe powder images are transferred by electrostaticattraction to a paper strip and the powder images thereon are fused toprovide a permanent print.

For a better understanding of the invention, as well as further objectsand features thereof, reference is made to the following detaileddescription to be read in connection with the accompanying drawing,wherein like components in the several views are identified by likereference numerals.

In the drawing:

FIG. 1 shows schematically a perspective view of one preferredembodiment of an alphanumerical printer in accordance with theinvention;

FIG. 2 shows schematically a perspective view of a second preferredembodiment of an electrostatic printer in accordance with the invention;

FIG. 3 is a separate elevational view of the character drum shown inFIG. 2;

FIG. 4 is a schematic diagram of a third embodiment of the invention;

lFlG. 5 is a detail of FIG. v4;

FIG. 6 is a further embodiment of the invention, shown schematically;and

FIG. 7 is a detail of FIG. 6.

`Referring now to FIG. l, the electrostatic printer comprises an endlessweb 10 supported between a pair of spaced rollers 11 and 12. Web 10 iscomposed of a flexible material of high resistivity such as Mylar orTeflon, the material being capable of holding an electrostatic image fora period which permits subsequent utili- Zation thereof by transfer toanother surface.

Supported above the upper portion of the web at a position substantiallytransverse thereto is a character drum, generally designated by numeral13. Drum 1? is rotatably mounted and driven at a constant angularvelocity by a suitable motor. Arranged across the drum is a bank ofidentical character rings 14, each containing a circumferential assemblyof raised-character metallic elements 15. One ring of characters isprovided for each column to be printed. The characters in each ringthereof are composed of alphabetical letters, numbers and other symbols,each representative of a different value of the applied information. Thedrum may be exactly normal to the continuous web, or slightly askew.This factor will be discussed later in the specification. "Ihe characterrings are slightly spaced from the web to define an air gap in which afield discharge may occur to effect an image transfer.

Supported below the web in alignment with the drum is an array ofstationary electrodes 16, one for each ring in the character drum, theelectrodes occupying corresponding positions. By means of an electrodepulsing supply repersented by block 17, the electrodes are sequentiallyactivated such that only one electrode is active at a time to permitelectrostatic recording at a corresponding position on the web. Inoperation, when a character on the ring representative of the inputinformation is angularly aligned with the activated electrode a fielddischarge is produced to form a charge pattern on the web having theshape of the selected character.

The manner by which the characters are selected and the electrodes areactivated is treated in greater detail in said copending application. Adisc 18 is attached to one end of the drum, the disc containing magneticindexing marks 19 in a circumferential arrangement at positionscorresponding to the character positions on the rings. As disclosed insaid applications, these marks are sensed by a magnetic head (not shown)to produce voltage impulses at time positions reflecting the angularpositions of the characters on the rings. A magnetic mark on the otherend of the drum cooperating with another pick-up head serves to indicatea full revolution of the drum.

In the electronic control system for the character drum described in thecopending application Electrostatic Recording of Information, thelogical circuitry requires a synchronous serial input at the specifiedprinting rate, whereas in the system described in the copendingapplication High Speed Electrostatic Alphanumerical Printer, informationmay be printed as received on a random basis, the operation beingasynchronous. Either circuit may be used in conjunction with thecharacter drum in the present invention. By increasing the cornplexityof the logical circuitry and providing a buffer storage system, theprinter can be made to record a line for every revolution of thecharacter drum rather than one digit or letter per revolution.

The direction of motion is counter-clockwise whereby the continuous webis iirst subjected to a pre-stressing potential before it arrives at thecharacter drum for recording. This is accomplished by means of a coronacharging station 20 positioned in advance of the character drum whichpre-stresses the web to a uniform potential below the critical stressvalue, such that a relatively small pulse at the recording station 13 issufficient to produce a field discharge effecting image transfer. Thecorona charging station 2i) also acts to equalize the charged on theweb, thereby erasing all previously recorded charges in preparation forthe next recording cycle.

The web leaving the character drum and carrying the electrostatic chargepattern enters a development section 2.1 of standard design in whichpowder is Howed over the latent electrostatic images, the powderadhering only to the charged areas. The powder is caused to fall on theimage layer as it turns about roller 12 and to move downwardly thereoverby gravity in a continuous stream, the powder being evenly distributedover the image. The operation and structure of the developer section ismore fully disclosed in the patent to Schaffert No. 2,576,047, issuedNovember 20, 1951.

t The resultant powder images formed on the web are transferred to apaper strip 22 which is fed from a suitable supply roll 23, the striptravelling lover a transfer roller 24 and being rewound on a take-uproller 25. The characters must be put on the web wrong reading and fromright to left so that they are right reading and left to right on thefinal paper support.

The transfer roller 24 is supported transversely with respect tothelower portion of the web intermediate the web rollers 11 and 12 and actsto carry the paper strip into momentary contact with the web; the weband strip moving in like directions at the same speed. The supply roller23 and take-up roller 25 are mounted below the web rollers l1 and 12,all of the rollers being supported in suitable bearings on a frame. Thusthe only point of contact between the paper strip 2-2- and the web 1i)is at the position of the transfer roller.

The transfer roller 24, which may be made of conductive rubber material,is connected to a voltage source 26 which functions to impress a chargeacross the region of the paper strip 22, engaging web 10. The magnitudeof the charge applied to the paper strip and the polarity thereof issuch as to overcome the adhesion of the powder particles to the imagearea on the web and to establish a greater tendency of the particles toadhere to the paper, thereby effecting a transfer o-f the powder image-to the paper strip. The charge applied to the paper strip by thetransfer roller is of opposite polarity to the charge on the developerpowder, the powder therefore being attracted to and retained by thepaper strip.

The powder image transferred to the paper strip is fused thereon byheating elements 27 of any suitable construction disposed in operativerelation to the strip between the transfer roller 24 and the take-uproller 25.

To remove residual powder from the web 10 after the transfer operationis completed and before it again enters the charging station for thenext recording, a rotary brush 2S is provided which engages the webagainst its roller 11. The brush acts to remove any powder adhering tothe insulating web which has not been previously transferred to thepaper strip, thus preparing the web for a fresh supply of powder. Thecleaning means may consist of any sui-table wiping or suction device andis preferably of the type disclosed in the patent to Turner et al. No.2,751,616, issued Iune 26, 1956. After the web has been cleaned ofresidual toner the charging station 2t) acts uniformly to charge the web191 to a pre-selected potential by means of corona wires.

In the event'the recording operation is carried out while the web ismoving continuously, it is then necessary slightly to skew the characterdrum 13 relative to the web to compensate for the web motion and therebyinsure that the courseof the printed line runs perpendicularly to theedges of the web. Alternatively, the rings on the drum may be staggeredrelative to each other for the same purpose, in which case the ydrumneed not be skewed. But if the web is held stationary during therecording of a line, then the character drum may be supported directlyacross the web without skewing. In this case, the body of the web andthe transfer strip are advanced in a stepwise manner a line at a time bya suitable indexing mechanism actuated upon completion of each line. Acommon drive maybe provided for said web and said strip to maintainsynchronous movement thereof.

Referring now to'FIGS. 2 and 3, there is illustrated another embodimentof the invention which is identical to that -shovvn in FIG. l, save forthe structure of the recording web, lthe `character drum and the relatedelectrodes. The web supported between rollers l1 and 12 is constituted-by an endless metal belt 30 having a thin insulating layer 36a of highsurface resistivity coated thereon. The metal belt is grounded throughthe supporting rollers l11 and 12 therefor. Rotatably supported abovethe upper section of web 30 is a character drum 31 havinga series ofcharacter rings 32 thereon similar Y one another.

in nature to the rings on the drum shown in FIG. 1. The rings are,however, electrically insulated from each other by insulating discs 33.Adjacent each ring and electrically connected thereto is a commutatorring 34. Fixedly mounted above the drum is an array of electrodes 35,each electrode being disposed in spaced relation to a respectivecommutator ring.

The arrangement is such that each character ring may be pulsedseparately, as distinguished from. the previously disclosed arrangementin which all of the character rings were electrically interconnected.The character rings on the drum, as best seen in FIG. 3, are in spacedrelation to the web layer Sdu, to define a rst air gap 36, andtheelectrodes 35 occupy spaced positions relative to the cornmutator rings34 to define a second air gap 37, The character drum is supported onbearings insulated from the ground.

Thus when a pulse is applied to an electrode 35 relative to ground, acorona discharge will proceed across both air gaps, the gap between thepulsing electrodes and the drum serving as a commutator connection,while the gap between the drum and the web functions as an electrostaticimage transfer region. The electronic control circuit responsive to theinput information to be recorded acts to apply the pulses totheelectrodes when the selected characters are angularly aligned withthe endless dielectriccoated metal belt.

The operation of the printer illustrated in FIGS. 2` and 3 is otherwiseidentical with that shown in FIG. l. The web is rst pre-stressed at thecorona station and after the electrostatic image is recorded it isdeveloped to form a powder image, which image is transferred to a paperstrip and fixed thereon. As indicated earlier, it is possible to print afull line in a single rotation of the character drum providing a bufferstorage system is employed to handle a line-at-a-time of information.

If the web is permitted to move continuously during the recordinginterval it will move a short distance forward. Since the characterimages will be formed randomly along the line during this period, thecharacters will go down in positions slightly staggered with respect toFor example, if the character drum is rotating at a frequency of 200revolutions per second and the web is travelling, say, at a rate of 3inches per second, the paper will advance 0.0Il5 inch. This then is themaximum 'displacement distance between adjacent characters. Forcharacters 0.1 inch high, that is roughly of typewriter size, such adisplacement would probably be noticeable and therefore objectionable.This can be obviated by moving the web intermittently in the mannerindicated previously, such that the web is stationary when recordingtakes place.

It is also possible, as shown in FIG. 4, to use a matrix or a pointarray type of character presentation which may be selectively pulsed insuch a'way as to simulate any alphanumerical character, thus eliminatingthe need for a moving character drum.

In FIG. 4, in place of the endless web, a rotary metal cylinder 38 isemployed which is coated with a layer 39 of material having a highresistivity for holding an electrostatic image. The cylinder moves in acounterclockwise direction and is'pre-stressed at the corona station 20.A stationary character printing station 40 is provided constituted by abank of recording heads 41 having electrode points or pins 42 which canbeselectively pulsed to provide a matrix type of presentation simulatingan alphanumerical character. One head is provided at each columnposition. As shown in the drawing, the characters are each formed by apattern of dots.

Each recording head 41 consists of a set of five flat faced pins 42 in arow maintained at a fixed distance from the surface of the cylinderlayer 39, the pins of the several heads running across the cylinder. Theindividual characters are built up by seven successive choices of thefive aoaavsr pins as the cylinder moves forward. An electronic pulsingcircuit is provided for each pin. Thus as the cylinder rotates, the pinsin the heads are selectively activated by input information in sevensuccessive steps to construct latent images of the appropriatecharacters on the cylinder surface.

A magnetic matrix and decoding unit may be used to buffer the pulsingcircuits to the pins and the information source. A description of a unitadaptable for this purpose as well as an electronic pulsing circuit forthe pins may be found in the article Burroughs Electrographic PrintingTechnique by Herman Epstein, March 1955- Proceedings of the WesternJoint Computer Conference (AIRE-IRE).

The latent images impressed electrostatically on the cylinder aredeveloped at the development section 21, and the resultant powder imageis transferred to a paper strip 22 in the manner described hereinabove.After the transfer operation, the cylinder is cleaned of residual tonerby the rotary brush 2S, and the surface is pre-stressed in preparationfor the next recording.

In FIGS. 4 and 5, the characters are built up of a point array in sevensuccessive. steps as the cylinder advances relative to the single row ofpins. Alternatively, each recording head 43, as shown in FIGS. 6 and 7,may consist of seven rows of pins 44, five in each row. This makespossible the formation of the character matrix in one step but involvesa more complex pulsing and decoding circuit. It is necessary to useseven coordinated decoding units whereby all seven rows of pins may beselectively pulsed at the same time to form the desired alphanumericalcharacter.

While there have been shown what are at present considered to bepreferred embodiments of the invention, it will be obvious that manychanges and modifications may be made therein without departing from theessential aspects of the invention. It is intended, therefore, in theappended claims to cover all such changes as fall within the true spiritof the invention.

What is claimed is:

1. An electrostatic apparatus for recording and printing alphanumericalinformation at high speed, said apparatus comprising a movable endlessrecording medium having an insulating surface of high resistivity forsustaining electrostatic charges, a character-forming station supportedin spaced relation to said insulating surface to define an air gaptherebetween and including character-forming conductive elements adaptedto produce latent electrostatic images on said medium when voltages areapplied thereto having an amplitude raising the electric field acrosssaid air gap above the critical stress value and thereby effecting afield discharge in said air gap, means operatively disposed with respectto said medium beyond said station to form powder images of said latentimages, and means operatively coupled to said medium to transfer saidpowder images onto a printing surface by electrostatic attraction.

2. An electrostatic apparatus for recording and printing alphanumericalinformation at high speed, said apparatus comprising an endlessrecording medium having an insulating surface of high resistivity forsustaining electrostatic charges, a character-forming station supportedin spaced relation to said insulating surface to define an air gaptherebetween and including characterforming conductive elements adaptedto produce latent electrostatic images on said medium when voltages areapplied thereto having an amplitude raising the electric eld across saidair gap above the critical stress value and thereby effecting a fielddischarge in said air gap, means to move said medium relative to saidcharacterforming station to form successive lines of latent imagesthereon, charging means operatively disposed with respect to said mediumin advance of said station to prestress same to a uniform potential andthereby erase previous charges, developer means operatively disposedwith respect to said medium beyond said station to form powder images ofsaid latent images, and means operatively coupled to said medium totransfer said powder images onto a paper strip by electrostaticattraction.

3. An electrostatic apparatus for recording and printing alphanumericalinformation at high speed, said apparatus comprising an endlessrecording medium having an insulating surface of high resistivity forsustaining electrostatic charges, a character-forming station supportedin spaced relation to said insulating surface to define an air gaptherebetween and including characterforming conductive elements adaptedto produce latent electrostatic images on said medium when voltages areapplied thereto having an amplitude raising the electric field acrosssaid air gap above the critical stress value and thereby effecting afield discharge in said air gap, means to move said medium relative tosaid characterforming station to form successive lines, charging meansoperatively disposed with respect to said medium in advance of saidstation to pre-stress same to a uniform potential and thereby eraseprevious charges, developer means operatively disposed with respect tosaid medium beyond said station to form powder images of said latentimages, and means operatively coupled to said medium to transfer saidpowder images onto a paper strip by electrostatic attraction, said lastnamed means including a paper strip movable in synchronism with saidmedium, a transfer roller for effecting engagement between said stripand said medium, and means to apply a potential to said transfer rollerto attract said powder image to said strip.

4. A high-speed apparatus for recording and printing alphanumericalinformation, said apparatus comprising a continuous belt of insulatingmaterial, a rotary character drum having a bank of like character ringsthereon, each ring containing a series of character-shaped raisedconductive elements in a circumferential arrangement, the respectivecharacters in the series being representative of different values ofincoming information, said drum being disposed across said belt and inspaced relation thereabove to define an air gap, an array of fixedelectrodes disposed below said belt at positions corresponding to thoseof said rings, means responsive to the value of incoming information toapply a voltage pulse between one of said electrodes and said rings whenthe characters thereon representative of said value are in angularalignment with said belt, said pulse having an amplitude raising theelectric eld across said air gap above the critical stress value toeffect a field discharge in said gap and thereby forming anelectrostatic latent image of the selected character on said belt at aposition in accordance with said electrode, means to move said beltrelative to said drum to form successive lines of characters thereon,charging means operatively disposed relative to said belt in advance ofsaid drum to prestress said belt to a uniform potential, a developersection operatively disposed relative to said belt at a position beyondsaid station to form powder images of said latent images, and meansoperatively coupled to said belt to transfer said powder images onto apaper strip by electrostatic attraction.

5. A high-speed apparatus for recording and printing alphanumericalinformation, said apparatus comprising a continuous belt of insulatingmaterial of high resistivity for sustaining electrostatic charges, arotary character drum supported substantially transversely relative tothe outer surface of said belt and having a bank of like character ringsthereon, each ring containing a series of character-shaped raisedconductive elements in a circumferential arrangement, the respectivecharacters in the series being representative of different values ofincoming information, said drum being disposed in spaced relation tosaid belt to define an air gap, an array of fixed electrodes disposedtransversely relative to the under surface of said belt at positionscorresponding to those of said rings, means responsive to the value ofincoming information to apply a voltage pulse between one of saidelectrodes and said rings when the characters thereon representative ofsaid value are in angular alignment with said belt, said pulse having anamplitude raising the electric field across said air gap above ythecritical stress value to effect a field discharge in said gap andthereby `forming an electrostatic latent image of the selectedcharacters on said belt at a position in accordance with said electrode,means to move said belt relative to said drum to form successive linesof characters thereon, charging means operatively disposed relative tosaid belt in advance of said drum to pre-stress said belt to a uniformpotential, a developer section operatively disposed relative to saidbelt at a position beyond said station to form powder images of saidlatent images, and means operatively coupled to said belt to transfersaid powder images onto a paper strip by electrostatic attraction.

6. A high-speed apparatus for recording and printing alphanumericalinformation, said apparatus comprising a continuous belt of insulatingmaterial of high resistivity for sustaining electrostatic charges, arotary character drum supported substantially transversely relative tothe outer surface of said belt and having a bank of like character ringsthereon, each ring containing a series of character-shaped raisedconductive elements in a circumferential arrangement, the respectivecharacters in the series being representative of different values ofincoming information, said drum being disposed in spaced relation tosaid belt to deline an air gap, an array of fixed electrodes disposedtransversely relative to the under surface of said belt at positionscorresponding to those of said rings, means responsive to the value ofincoming information to apply a voltage pulse between one of saidelectrodes and said rings when the characters thereon representative ofsaid value are in angular alignment with said belt, said pulse Having anamplitude raising the electric ield across said air gap above thecritical stress value to effect a eld discharge in said gap and thereby`forming an electrostatic latent image of the selected characters onsaid belt at a position in accordance with said electrode, means to movesaid belt relative to said drum to form successive lines of charactersthereon, charging means operatively disposed relative to said belt inadvance of said drum to pre-stress said belt to a uniform potential, adeveloper section operatively disposed relative to said belt at aposition beyond said station to form powder images of said latentimages, means operatively coupled to said belt to transfer said powderimages onto a paper strip by electrostatic attraction, said last-namedmeans including a paper strip movable in synchronism with said belt, atransfer roller for eecting engagement between said strip and said belt,and means to apply a potential to said transfer roller attracting saidpowder image to said strip.

7. Apparatus, as set forth in claim 6, further including means to fusesaid powder image onto said strip.

8. A high-speed apparatus for recording alphanumerical information, saidapparatus comprising a continuous metal belt having an outer layer ofinsulating material thereon for sustaining electrostatic charges, arotary character drum supported substantially transversely relative tosaid belt in spaced relation thereto to dene an electrostatic air gap,said drum having a bank of like character rings thereon insulated fromeach other and a bank of commutator rings each adjacent to and inelectrical contact with a respective character ring, each ringcontaining a series of character-shaped conductive elcments in acircumferential arrangement, the respective characters in the seriesbeing representative of different values of incoming information, anarray of Xed electrodes aligned with said commutator rings and spacedtherefrom to form a commutating air gap, and means responsive to thevalue of incoming information to apply a voltage pulse to a selectedelectrode relative to said metal belt when the characters on said drumrepresentative of said value are in angular alignment with said belt,said pulse having a magnitude raising the electric eld above thecritical stress value and effecting a eld discharge between saidcharacters and said insulating layer to form an electrostatic latentimage thereon.

9. A high-speed apparatus for recording and printing alphanumericalinformation, said apparatus comprising a continuous metal belt having anouter layer of insulating material thereon for sustaining electrostaticcharges, a rotary character drum supported substantially transverselyrelative to said belt in spaced relation thereto to dene anelectrostatic air gap, said drum having a bank of like character ringsthereon insulated from each other and a bank of commutator rings eachadjacent to and in electrical contact with a respective character ring,each ring containing a series of character-shaped conductive elements ina circumferential arrangement, the respective characters in the seriesbeing representative of different values of incoming information, anarray of xed electrodes aligned with said commutator rings and spacedtherefrom to form a commutating air gap, means responsive to the valueof incoming information to apply a voltage pulse to a selected electroderelative to said metal belt when the characters on said drumrepresentative of said value are in angular alignment with said belt,said pulse having a magnitude raising the electric eld above thecritical stress value and effecting a eld discharge between saidcharacters and said insulating layer to form an electrostatic latentimage thereon, and means to form a powder image of said latent image andto transfer same to a paper strip.

l0. High-speed apparatus for recording and printing alphanumericalinformation comprising a rotary metal cylinder having a dielectric layercoated thereon for sustaining electrostatic charges, a characterrecording station including a bank of stationary character headsextending across said cylinder, each head including a row of conductivepoint electrodes disposed in spaced relation to said dielectric layer todeine an air gap, means to rotate said cylinder relative to saidrecording station, means selectively to pulse said point electrodesduring movement of said cylinder in accordance with the value of appliedinformation to be recorded, said pulse having an amplitude raising theelectric field across said air gap above the critical stress value toeifect a field discharge across the gap thereby to form an electrostaticpoint charge pattern on said layer simulating a character representativeof said value, developer means to form powder images of said chargepatterns, means to transfer said powder images to a paper strip byelectrostatic attraction, and prestressing means Ato return said layerat a uniform potential after said transfer operation.

ll. High-speed apparatus for recording and printing alphanumericalinformation comprising a rotary metal cylinder having a dielectric layercoated thereon for sustaining electrostatic charges, a characterrecording station including a bank of stationary character headsextending across said cylinder, each head including a row of conductivepoint electrodes disposed in spaced relation to said dielectric layer todene an air gap, means to rotate said cylinder relative to saidrecording station, means selectively to pulse said point electrodesduring movement of said cylinder in accordance with the value of appliedinformation to be recorded, said pulse having an amplitude raising theelectric eld across said air gap above the critical stress value toeffect a eld discharge across the gap thereby to form an electrostaticpoint charge pattern on said layer simulating a character representativeof said value, developer means operatively disposed relative to saidcylinder beyond said station to form powder images of said chargepatterns, means including a charged transfer roller to transfer saidpowder images to a paper strip by electrostatic attraction, prestressingmeans in advance of said station to return said layer at a uniformpotential after said transfer operation, and rotary brush means inadvance of said pre-stressing means to clean said cylinder of residualpowder.

12. High-speed apparatus `for recording and printing alphanumericalinformation comprising a rotary metal cylinder having a dielectric layercoated thereon for sustaining electrostatic charges, a characterrecording station including a bank of stationary character heads eX-tending across said cylinder, each head including a rectangular array ofconductive point electrodes in spaced relation to said dielectric layerto define an air gap, said array being formed by parallel rows of pins,means to rotate said cylinder relative to said recording station, meansselectively to pulse said pins in accordance with the value of appliedinformation to be recorded, said pulse having an amplitude raising theelectric field across said air gap above the critical stress value toeffect a field discharge across the gap thereby to form an electrostaticpoint charge pattern on said layer simulating a character representativeof said value, developer means to form a powder image of said chargepattern, means to transfer said powder images by electrostatic attraction to a paper strip, and means to erase said charge pattern beforesaid cylinder reaches said station.

13. An electrostatic apparatus for recording and printing alphanumericalinformation at high speed, said apparatus comprising a movable endlessrecording medium having an insulating surface of high resistivity forsustaining electrostatic charges, a character forming station includinga set of conductive character forming elements supported relative to oneside of said surface, a set of conductive backing elements supportedrelative to the other side of said surface, one of said sets beingspaced from said surface to form an air gap therebetween, electrostaticimages of said character forming elements being produced on said surfacewhen voltages are applied to said character forming elements relative tosaid backing elements effecting a field discharge in said air gap, meansoperatively disposed with respect to said medium beyond said station toform powder images of said latent images, and means operatively coupledto said medium to transfer said powder images onto a printing surface byelectrostatic attraction.

14. An electrostatic apparatus for recording and printinc'alphanumerical information at high speed, said apparatus comprising amovable endless recording medium having an insulating surface of highresistivity for sustaining electrostatic charges, a character formingstation including a set of conductive character forming elementssupported relative to one side of said surface, a set of conductivebacking elements supported relative to the other side of said surface,one of said sets being spaced from said surface to form an air gaptherebetween, electrostatic images of said character forming elementsbeing produced on said surface when voltages are applied to saidcharacter forming elements relative to said backing elements effecting afield discharge in said air gap, means operatively disposed with respectto said medium beyond said station to form powder images of said latentimages, and means operatively coupled to said medium to transfer saidpowder images onto a printing surface by electrostatic attraction, saidprinting surface being formed of a material having a resistivity whichis low relative to that of said recording medium.

15. An electrostatic apparatus, as set forth in claim 14, wherein saidrecording medium has a surface formed by a flexible plastic and saidprinting surface is formed of paper.

16. An electrostatic apparatus, as set forth in claim 14, wherein saidrecording medium is formed of a coated paper, which coating imparts highresistivity thereto, and said printing surface is formed of uncoatedpaper.

17. An electrostatic apparatus for recording and printing alphanumericalinformation at high speed, said apparatus comprising a movable endlessrecording medium having an insulating surface of high resistivity forsustaining electrostatic charges, a character forming station includinga conductive character forming element supported relative to one side ofsaid surface, a conductive backing element supported relative to theother side of said surface, one of said elements being spaced from saidsurface to form an air gap therebetween, electrostatic images of saidcharacter forming element being produced on said surface when a voltageis applied thereto relative to said backing element effecting a fielddischarge in said air gap, means operatively disposed with respect tosaid medium beyond said station to form powder images of said latentimages, and means operatively coupled to said medium to transfer saidpowder images onto a printing surface by electrostatic attraction.

References Cited in the file of this patent UNITED STATES PATENTS1,865,610 Blair July 5, 1932 2,715,360 Brown Aug. 16, 1955 2,726,940Buhler Dec. 13, 1955 2,777,745 McNaney Jan. 15, 1957 2,825,814 WalkupMar. 4, 1958 FOREIGN PATENTS 1,112,180 France Nov. 9, 1955 734,909 GreatBritain W Aug. 10, 1955 OTHER REFERENCES General Electric Review, July'1952, pp. 20, 2l, 22 and 61.

